1. Field of the Invention
The present invention relates to a bearing assembly with a thrust bearing for receiving a load in a thrust direction and a radial bearing for receiving a load in a radial direction set up as a single body, and more particularly to a bearing assembly which is most suited to use with a flat motor.
2. Description of the Related Art
Examples of flat motors for the prior art will now be described. First, an description will be given with reference to FIG. 5 of a first example of a conventional motor which is constructed from of a rotor 21 and a stator 31. At this rotor 21, a rotor magnet 22 which is magnetized in the planar direction is attached to the rotor yoke 23, with this rotor yoke 23 then being attached to the rotating axis 25 via a sleeve 24.
The stator 31 is constructed from a coil 32 and a back yoke 33 to which this coil is fixed, at the center of which there is a bearing housing containing two levels of ball bearings 34. The rotor 21 freely rotates about the stator 31 while being supported by the ball bearings 4. Two levels of ball bearings are used in this example of a conventional motor because the stator 31 supports the rotor 21.
As this kind of two level ball bearing construction was expensive, the example of a conventional motor shown in FIG. 6 was proposed as a way of reducing costs. In this motor using a second conventional example the first layer of ball bearings 34 remains but the other level has been changed for an oil containing alloy bearing 36. Also, in a third example in a conventional motor, as is shown in FIG. 7, there is only an oil containing alloy bearing 36 at the first level and a ball positioned at a hole 37 in the center of the rotating axis 25. The oil containing alloy bearing 36 takes the load in the radial direction and the ball 37 takes the load in the thrust direction.
In the above, three examples of the conventional technology are described. However, with regards to the rotor magnet 22, if a rare earth magnet having a strong magnetic attraction was used as the moving magnet, this strong magnetic attraction could not be overcome in the bearing assembly for the prior art. It also proved to be difficult to construct a thin bearing using this kind of two layered construction. Further, if the assembly is made thin, the precision with which the bearing rotates axially is degraded.
As this invention sets out to solve the problems encountered in the prior art, it's object is to provide a bearing assembly where the magnetic attraction of the rotor magnet can be overcome and which can have a thin construction.